A psi ball is claimed to be a manifestation of gathered psychic energy that is formed into a ball shape by a practioner of psionics, to be used in a variety of ways.

There have been no controlled scientific studies showing support for the existence of psi balls. Furthermore, the existence of parapsychological skills, including the creation of psi balls, is viewed with skepticism by most mainstream scientists (see pseudoscience).

Psi balls are said to be capable of performing many different tasks, such as healing, telekinesis, or sending short telepathic messages. The energy is said to come from both inside the mind of the practitioner and also from a variety of external sources, such as the Sun, Moon and the Earth.

Those who believe in their existence assert that they can be formed in a variety of different shapes, sizes and temperatures, depending on the creator's wishes. Psi balls may also be formed at any location, even if the location is external to the creator's vision.

Many believers claim that psi balls are typically invisible and therefore may only be felt. However, people who claim to be skilled psychics are said to be able to construct psi balls that are visible to others. Additionally, people who claim to be sensitive to auras also say they have the ability to detect invisible psi balls.

In psionics, the creation of psi balls is often seen to be one of the first steps a beginner may take in developing their psychic skills.